1. Field of the Invention
The present invention relates to a structure of an exhaust pipe connected to an internal combustion engine.
2. Description of the Related Art
Generally, vibrations generated by the internal combustion engine in operation are transmitted to the exhaust pipe connected to the internal combustion engine. A load caused by these vibrations is thus imposed on the exhaust pipe, which disadvantageously lowers durability and reliability of the exhaust pipe. In addition, the vibrations are transmitted through a support member for the exhaust pipe to a vehicle body, causing undesirable noise and vibrations in the vehicle interior. Therefore, in order to suppress transmission of exhaust pipe vibrations or absorb the vibrations, a widely used exhaust pipe structure has: an exhaust pipe including plural separate exhaust pipes connecting in series to join an exhaust manifold of the internal combustion engine; and a universal joint, such as spherical joint, used for connecting the separate exhaust pipes to allow them to bend flexibly at the joint. An example of this type of exhaust pipe structure is shown in Japanese patent application publication JP-A-2002-160536. The exhaust pipe includes a first exhaust pipe, a second exhaust pipe, and a tail pipe, the first and second exhaust pipes being joined by a spherical joint. The exhaust pipe thus formed inhibits transmission of vibrations from the internal combustion engine to the exhaust pipe. This improves durability and reliability of the exhaust pipe, while suppressing undesirable noise or vibrations in the vehicle interior.
The aforementioned exhaust pipe structure is designed such that the exhaust pipe is provided with heavy components, such as a muffler and a catalytic converter, imposing a load on the universal joint connecting the separate exhaust pipes. This can cause the exhaust pipe to be displaced from its normal position in the static state. When the vehicle travels off-road or over an uneven road surface, the exhaust pipe, supported at the position out of the normal mounting position, can be excessively displaced beyond the allowance range. Thus, the exhaust pipe tends to interfere with peripheral components. Preferably, the exhaust pipe is supported at a position adjacent to the universal joint, so that the exhaust pipe is prevented from being displaced from the normal position. Nonetheless, supporting the exhaust pipe in this preferred manner is sometimes difficult mainly due to insufficient body strength at the position adjacent to the universal joint. As described above, which part of the exhaust pipe to be supported and where to locate the universal joint depend on constraints of the vehicle body, such as body structure. This could result in difficulty in supporting the exhaust pipe at its normal position in the static state.